Multi-bend steerable mapping catheter

RELATED APPLICATION DATA

0001The present application is a continuation of U.S. patent application Ser. No. 12/838,285, filed Jul. 16, 2010, now U.S. Pat. No. 8,229,538; which is a continuation of U.S. patent application Ser. No. 11/470,132, now U.S. Pat. No. 7,774,039, the entire disclosures are incorporated herein by reference.

FIELD OF INVENTION

0002This invention pertains to electrophysiology (“EP”) mapping catheters and, more particularly, to a multi-bend, steerable catheter configured for accessing and mapping the high right atrium and coronary sinus via groin access and the superior vena cava.

BACKGROUND

0003Electrophysiology is the study of electrical impulses through the heart and is focused primarily on diagnosing and treating arrhythmias, conditions in which electrical impulses within the heart vary from the normal rate or rhythm of a heartbeat. The most common arrhythmia is atrial fibrillation (AF), which is characterized by rapid, disorganized contractions of the heart's upper chambers, the atria. AF results from abnormal electrical impulses propagating through aberrant myocardial tissue pathways, which leads to ineffective pumping of the blood through the heart, as well as other complications. Atria flutter (AFL), another type of arrhythmia, is characterized by a rapid beating of the atria. Unlike AF, AFL arises from a single electrical wave that circulates rapidly throughout the right side of the heart. Since this arrhythmia can arise from multiple electrical sites, effective treatment requires electrical isolation of the aberrant signal sites, thereby forcing the heart's normal conduction pathway to take over.

0004The practice of interventional electrophysiology for treating arrhythmias, such as AF and AFL, generally involves inserting specialized catheters into a patient's vasculature and navigating the distal (or “working”) end of the catheters into the patient's heart chambers to identify (or “map”) the locations of heart tissue that are a source of the arrhythmias. The mapping of the heart's electrical activity is typically accomplished using one or more pairs of electrodes, each pair spaced apart axially along the working end of the catheter. Following or in conjunction with the mapping procedure, the attending physician may use an ablation catheter to disable (or “ablate”) the tissue containing the aberrant signal(s) or signal pathway(s), thereby restoring the heart to its normal rhythm.

0005While catheters may be provided with combined mapping and ablation functionalities, separate mapping and ablation catheters are more typically used, which allows for much greater capability of their respective functions. For example, electrical activity is normally mapped using much smaller electrodes (in surface area) than are used for performing ablation procedures. Because there is significantly less current transmitted through a mapping electrode circuit than through an ablation circuit, the lead wires that connect the mapping electrodes to processing circuitry (e.g., via a pin connector in the catheter handle) are much smaller than are used to couple ablation electrodes to an RF generator. As such, a much greater number of electrodes may be provided on a mapping catheter than on an ablation catheter having a same or similar profile.

0006For AFL mapping procedures (as well as for some AF procedures), it is important to map the electrical activity in both the coronary sinus (CS) and the right atrium (RA), especially the region of the high right atrium (HRA). Currently, to map both the CS and the RA, a pre-shaped, non-steerable, mapping catheter having two sets of electrodes is inserted through a jugular vein at the base of the patient's neck, through the superior vena cava (SVC), and into the RA, where it bends (or “banks”) off of the lower portion of the atrial chamber (i.e., over the isthmus region) and into the CS. While functional for mapping the respective RA and CS, this type of catheter has certain drawbacks. For example, because it passes across the lower atrial chamber, maneuvering the mapping catheter for achieving proper electrical contact in the HRA can be difficult. Further, since most ablation catheters used for AFL and AF interventional procedures are inserted through the groin and inferior vena cava (IVC), and are maneuvered to ablate tissue in the isthmus region of the lower atrial chamber, the mapping catheter extending across the isthmus can block and interfere with the ablation catheter. Plus, the patient and attending physician must cope with having two different access ports into the patient's venous system (i.e., both through the jugular and through the groin), making simultaneous control of the respective mapping and ablation catheters more difficult, and increasing the chances of related complications and patient discomfort.

0007While there are diagnostic catheters available for mapping the RA and HRA through groin access and the IVC, these typically form a complete distal end loop that encircles the atrial chamber, with a small tail segment for slight penetration into the ostium of the CS. The loop portion extends over the isthmus region in the lower right atrium (LRA), interfering with the ablation catheter, and the limited penetration of the CS results in corresponding limited CS mapping data.

0008Thus, it would be desirable to provide a diagnostic catheter that may be better positioned for mapping both the HRA and the CS, which is inserted through the groin and IVC, without blocking the isthmus.

SUMMARY OF THE INVENTION

0009In accordance with one embodiment, an electrophysiology catheter includes an elongate flexible shaft having a steerable distal section and a prolapsing section located proximally of the distal section. A first set of electrodes are carried on the steerable distal section, and a second set of electrodes are carried on the prolapsing section. By way of example, the electrophysiology catheter may be a diagnostic catheter, with the first and second sets of electrodes comprising respective first and second sets of mapping electrode pairs.

0010The catheter shaft comprising a soft outer tubing that has an embedded reinforcing braid extending from the handle through a main body section of the catheter to increase its hardness. The reinforcing braid terminates in a transition region between the main body section and the prolapsing section, so that the outer shaft of the prolapsing section is much softer, facilitating its prolapsing against the HRA. The distal section may be steered bi-directionally by actuating pull wires (e.g., using a steering mechanism in the catheter handle) having distal ends attached to opposing sides of a flat, resilient center support member positioned in an interior of the distal section. The steering assembly also includes a tightly wound, highly flexible compression coil that extends from the handle to the support member through a central lumen of the outer shaft, with the pull wires positioned within an inner lumen of the flexible coil. To facilitate prolapsing of, and provide structural support to, the prolapsing section, the cross-section of the compression coil changes from generally circular to generally oval or “flattened” within the prolapsing section, prior to the transition to the distal section.

0011In accordance with another embodiment, a method of mapping conductive pathways in a patient's heart tissue includes the steps of (i) inserting an elongate flexible catheter through an access location proximate the patient's groin and into a patient's venous system, (ii) advancing the catheter through the patient's inferior vena cava and into the right atrium, (iii) directing a steerable distal section of the catheter into the coronary sinus, and (iv) further advancing the catheter to cause a prolapsing section thereof located proximally of the distal section to prolapse against the high right atrium. The method may further include one or more of (v) applying a back-steering force to anchor the distal section in the coronary sinus prior to further advancing the catheter to cause the prolapsing section to prolapse against the HRA wall, (vi) mapping electrical pathways in the patient's coronary sinus using one or more electrode pairs carried on the distal section, and (vii) mapping electrical pathways in the patient's high right atrium using one or more electrode pairs carried on the prolapsing section.

0012Other and further features and advantages of embodiments of the invention will become apparent from the following detailed description, when read in view of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

0013Embodiments of the invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which:

0014<figref idref="DRAWINGS">FIG. 1</figref> is a perspective image of a distal end portion of a diagnostic mapping catheter constructed according to one embodiment.

0015<figref idref="DRAWINGS">FIG. 2</figref> is a perspective image of the catheter of <figref idref="DRAWINGS">FIG. 1</figref> with an internal distal steering support member being deflected to form a curved loop segment out of the catheter distal end.

0016<figref idref="DRAWINGS">FIG. 3</figref> is a schematic image of the catheter of <figref idref="DRAWINGS">FIG. 1</figref>.

0017<figref idref="DRAWINGS">FIG. 3A</figref> is a cross-sectional end view taken along dashed line A-A in <figref idref="DRAWINGS">FIG. 3</figref>.

0018<figref idref="DRAWINGS">FIG. 3B</figref> is a cross-sectional end view taken along dashed line B-B in <figref idref="DRAWINGS">FIG. 3</figref>.

0019<figref idref="DRAWINGS">FIG. 3C</figref> is a cross-sectional end view taken along dashed line C-C in <figref idref="DRAWINGS">FIG. 3</figref>.

0020<figref idref="DRAWINGS">FIG. 4</figref> is a perspective view of the catheter of <figref idref="DRAWINGS">FIG. 1</figref> extending through the respective inferior vena cava and right atrium, and into the coronary sinus of a three dimensional model of a human heart, with a prolapsed section of the catheter shown slightly torqued and leveraged against the wall of the high right atrium.

0021<figref idref="DRAWINGS">FIG. 5</figref> and <figref idref="DRAWINGS">FIG. 6</figref> are additional perspective views of the catheter positioned in the heart model of <figref idref="DRAWINGS">FIG. 4</figref>.

DETAILED DESCRIPTION

0022<figref idref="DRAWINGS">FIG. 1</figref> depicts a distal portion of a diagnostic catheter <b>20</b> constructed in accordance with one embodiment of the invention. The catheter <b>20</b> comprises an elongate, flexible shaft <b>21</b> extending from a proximal handle (not shown), as is well-known in the art for electrophysiology catheters. The catheter shaft <b>21</b> generally includes a steerable distal section <b>22</b>, and a prolapsing section <b>24</b> located immediately proximal of the distal section <b>20</b>, which distal and prolapsing sections <b>22</b> and <b>24</b> are sized and configured for placement in a patient's coronary sinus (CS) and high right atrium (HRA), respectively. As best seen in <figref idref="DRAWINGS">FIG. 3</figref>, the catheter <b>20</b> is a “twenty pole” catheter, with ten electrodes <b>28</b> (comprising five electrode pairs <b>30</b>) carried on the steerable distal section <b>22</b> for mapping in the CS, and another ten electrodes <b>29</b> (comprising five electrode pairs <b>32</b>) carried on the prolapsing section <b>24</b> for mapping the HRA. The electrodes <b>28</b>, <b>29</b> are coupled to respective lead wires that extend through the interior of the catheter shaft and are preferably bundled together (reference no. <b>36</b> in <figref idref="DRAWINGS">FIGS. 3A-3B</figref>) in a well-known manner.

0023In accordance with one aspect of the invention, the catheter shaft <b>21</b> is sized and configured for accessing the venous system through the patient's groin, and for navigation up the inferior vena cava (IVC) (reference no. <b>48</b> in <figref idref="DRAWINGS">FIGS. 4-6</figref>) and into the right atrium. Using a standard bi-directional steering support member embedded in the distal section <b>22</b> (described below in greater detail), the distal section <b>22</b> is guided into the CS. By way of illustration, <figref idref="DRAWINGS">FIG. 2</figref> shows the distal section <b>22</b> of the catheter shaft <b>21</b> formed into a three-quarter loop <b>25</b> by tensioning of the steering member. As seen in <figref idref="DRAWINGS">FIGS. 4-6</figref>, once the catheter distal section <b>22</b> is positioned in the CS <b>44</b>, the physician applies a “back steering” force on the steering mechanism so that the distal section <b>22</b> will become anchored in the CS <b>44</b>. The catheter <b>20</b> is then pushed forward by the physician to cause the prolapsing section <b>24</b> to “prolapse” in an arching loop lying against the wall of the HRA <b>46</b>. It will be appreciated that the prolapsing section <b>24</b> is slightly torqued (best seen in <figref idref="DRAWINGS">FIG. 6</figref>) as the distal section <b>22</b> positioned in the CS is not in the same plane as the prolapsing section <b>24</b> lying across the HRA wall, which provides a more stable positioning of the prolapsing section <b>24</b>.

0024With reference to <figref idref="DRAWINGS">FIGS. 3</figref>, <b>3</b>A, <b>3</b>B, and <b>3</b>C, the steering assembly includes a flat, resilient center support member <b>40</b> positioned in an interior of the catheter distal section <b>22</b>. The support member may be actuated using a well-known steering mechanism (not shown) in the handle by a pair of pull wires <b>34</b> having distal ends secured on opposing sides of the steering member <b>40</b>. As seen in <figref idref="DRAWINGS">FIG. 3A</figref>, a “flattened” Kevlar-reinforced tube <b>42</b> is used to constrain the steering wires <b>34</b> against the center support member <b>40</b>. By way of non-limiting example, the steering assembly in the diagnostic catheter <b>20</b> may be similar or identical that used in the Blazer catheter manufactured and distributed by Boston Scientific (www.bostonscientific.com).

0025The catheter shaft <b>21</b> comprises a relatively soft outer tubing <b>33</b> with an embedded braid <b>31</b> extending through the main body section <b>26</b>. The braid <b>31</b> terminates in a transition region <b>50</b> between the main body section <b>26</b> and the prolapsing section <b>24</b>, so that the outer tubing <b>33</b> of the shaft <b>21</b> in the prolapsing section <b>24</b> is relatively soft (e.g., with a hardness of approximately 35D in one embodiment) compared to shaft of the main body section <b>26</b> (e.g., with a hardness of approximately 72D in one embodiment). The relatively soft outer shaft enables the prolapsing section <b>24</b> to readily prolapse into the HRA when the distal section is anchored in the CS. The stiffer outer shaft <b>33</b> of the main body section <b>26</b> also facilitates prolapsing of the prolapsing section <b>24</b> against the HRA wall.

0026A cross section of the prolapsed section <b>24</b> is preferably substantially circular about its outer diameter. Residing in an interior lumen <b>39</b> of the outer tube <b>33</b> is a tightly wound, flexible compression coil <b>38</b> that constitutes part of the steering assembly. The coil <b>38</b> also provides a highly flexible structure for facilitating prolapsing of the prolapsing section <b>24</b> into (and against the wall of) the HRA. The coil <b>38</b> may be made of a stainless steel and preferably extends throughout the catheter body <b>21</b>, i.e., from the handle to the center support member <b>40</b> in the distal section <b>22</b>. The cross-section of the coil <b>38</b> preferably changes from a substantially circular shape in the main body section <b>26</b> to a substantially oval or flattened shape in the transition region <b>50</b> between the main body and prolapsing sections <b>26</b> and <b>24</b> in order provide directionality and enhanced torque of the prolapsing section <b>24</b>. A hinge joint (not shown) may optionally be built into a transition region <b>52</b> located between the prolapsing section <b>24</b> and distal section <b>22</b>, to further facilitate prolapsing of the prolapsing section <b>24</b> against the wall of the HRA.

0027It will be appreciated that the diagnostic catheter <b>20</b> will typically be used in conjunction with AFL ablation procedures in order to access bi-directional block across the isthmus, without interfering with the ablation catheter during the creation of an isthmus lesion. The catheter <b>20</b> may also be used for AF procedures, where it is important for the physician to map the electrical activity in the CS as well as the HRA. Because the catheter <b>20</b> is positioned through groin access and the IVC, and in particular because the prolapsing section <b>24</b> is torqued against the wall of the HRA, maneuvering for achieving solid electrical contact on the wall of the HRA is much easier than in previously existing RA mapping catheters.

0028The forgoing illustrated and described embodiments of the invention are susceptible to various modifications and alternative forms, and it should be understood that the invention generally, as well as the specific embodiments described herein, are not limited to the particular forms or methods disclosed, but to the contrary cover all modifications, equivalents and alternatives falling within the scope of the appended claims.